We sighted this bird several times in our walk all over that side of red Hill. At one point it flew very low and fast close to us chasing away a magpie. For the most part it was getting hassled by Currawong. Having reviewed the entry in the bird book and having seen it last week I've no doubt it's a hobby. At one point when it was flying above us we saw very clear that prominent bend in the wings. As well as this style of flying. Unfortunately because everytime we saw it was was flying extremely fast and usually dipping below our line of sight over hills or trees etc this was the only clear image.